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    <title>Document</title>
    <script>
        // join 把数组转换为字符串
        var arr = ['pink', 'hotpink', 'deeppink'];
        var str = arr.join('-');
        console.log(str);
        // split 把字符串 分割 转换为数组
        var str1 = 'pink-hotpink-deeppink';
        var arr1 = str1.split('-');
        console.log(arr1);
        // 字母大小写转换   toUpperCase 把字母转换为大写   toLowerCase 把字母转换为小写
        var str2 = 'andy';
        console.log(str2.toUpperCase());
        var str3 = 'ANDY';
        console.log(str3.toLowerCase());
    </script>
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